Since 1995, working with Environment Canada colleagues (e.g., Ralf M Staebler et al.) we have pursued research concerning long-term carbon dioxide cycling at the mixed deciduous forest of Camp Borden, Ontario, Canada.  The Borden tower is part of the AmeriFlux network.  Our approach is to investigate the edaphic, physiological and atmospheric controls on carbon cycling in forest ecosystems.  The results of field investigations are integrated in numerical modeling systems to infer the forest carbon sequestration capability in response to local and regional environmental change.  To date, our research has shown that temperate forest ecosystems in southern Canada effectively sequester atmospheric carbon dioxide at rates ranging from 100 to 400 gC per m² per year. Climate perturbations such as severe drought and features such as early spring thawing and length of growing season are key controls on the amount of carbon that the Borden forest can consume. Quality of solar irradiance, namely levels of diffuse iradiance, reaching the forest canopy is another variable controlling the manginute of carbon assimilation by the forest.  In connection to carbon cycling research, we have also investigated the fraction of photosynthetically fixed carbon released back to the atmosphere in the form of isoprene.  Under well rainfed conditions, forest ecosystems re-emit approximately 2 percent of the photosynthetically consumed carbon in the form of isoprene. Our research has demonstrated that this percentage could increase to 10 percent if forest ecosystems remain under the influence of droughts. Our group is continuing carbon cycling research at the mixed decidious forests in the Piedmont of central Virginia, the Florida Everglades mangrove forests, and the salt marshes in the eastern shore of Virginia.